$string =~ $regexp works if $regexp contains a regular expression. It doesn't in your case. "s/.../.../" is the Perl substitution operator, not a regular expression.

If given strings, the best way I can think of doing a substitution is:

$regexp = "a";
$subst  = "b";
$global = 1;

if ($global) {
   $string =~ s/$regexp/$subst/g;
} else {
   $string =~ s/$regexp/$subst/;
}

# (?i...) can be used in $regexp for /.../i
# (?m...) can be used in $regexp for /.../m
# (?s...) can be used in $regexp for /.../s
# (?x...) can be used in $regexp for /.../x
# /g cannot be stored in $regexp, thus the need for $global.
# /e cannot be stored in $regexp.

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In reply to Re: Exec'ing a regex stored in a scalar variable by ikegami
in thread Exec'ing a regex stored in a scalar variable by brycen

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